If you look closely, it seems the only spiky bits on Smokescreen are the big blue piece, while the rest of him looks to remain mostly faithful to the season 2 look. Its Beast Hunters Smokescreen and Season 2 Smokescreen all in one.

Is it removable? I can see it in robot mode, but it looks molded in on vehicle mode to me.

Looking at it, I'd say that it clips onto the edge of the doors in vehicle mode. If those are his real doors on his back in bot mode, then they must detach from the armour, and it's obvious that it detaches from the bonnet, so....